1. Field of the Invention
The present invention relates to a rotary head drum apparatus having short wirings that is able to transfer higher radio frequency signals. In addition, the present invention relates to a helical scanning type magnetic recording and/or reproducing apparatus using such rotary head drum apparatus.
2. Description of Related Art
A conventional rotary head drum apparatus that is used for a magnetic recording and/or reproducing apparatus of helical scanning type has a pair of recording heads and a pair of reproducing heads, wherein each pair of recording heads and reproducing heads are disposed at positions different by 180° on a rotary drum, respectively. A recording signal and a reproducing signal are transferred through a rotary transformer (for example, see Japanese Patent Laid-Open Publication No. 2001-160201).
The magnetic recording and/or reproducing apparatus disclosed in the above mentioned Publication has a Read After Write (RAW) function while reproducing recorded information from a tape shaped recording medium so as to check whether or not the information is correctly recorded thereto when recording the information thereto. To accomplish the RAW function, the rotary transformer has a recording signal channel and a reproducing signal channel for supplying recording signals to the recording heads and for deriving reproducing signals from the reproducing heads, respectively.
Next, a signal transferring portion of the magnetic recording and/or reproducing apparatus will be described. As shown in FIG. 1, a pair of a recording head 4A and a reproducing head 5A and a pair of recording head 4B and a reproducing head 5B are disposed at positions different by 180° on a rotary drum. As shown in FIG. 4, whenever the rotary drum rotates by 180°, the pair of the recording signal channel ch A and the reproducing signal channel ch A and the pair of the recording signal channel ch B and the reproducing signal channel ch B alternately operates.
In FIG. 9, the rotary transformer is designated by reference numeral 7. The rotary transformer 7 transfers (supplies and receives) signals of individual channels. The rotary transformer 7 has recording signal channels 8a and 8b for supplying recording signals to the recording heads 4A and 4B, reproducing signal channels 9a and 9b for receiving signals from the reproducing heads 5A and 5B, a power supply channel 10 for supplying a power to head amplifiers, and short-circuit rings 11 and 11 as shield channels for preventing a cross talk of the power supplying channel 10 from taking place in other signal channels. Each of the channels 8a, 8b, 9a, 9b, 10 and the short-circuit rings 11 and 11 (of the rotary transformer 7) is composed of rotor side coils 8ar, 8br, 9ar, 9br, 10r, and 11r and stator side coils 8as, 8bs, 9as, 9bs, 10s, and 11s. The rotor side coils and the stator side coils of each of the channels and short-circuit rings are disposed in coaxially formed ring-shaped grooves.
The signal transferring portion is structured as shown in FIG. 8. Recording signals are transferred from recording amplifiers 19a and 19b to the recording heads 4A and 4B through the recording signal channels 8a and 8b, respectively. Reproducing signals are transferred from the reproducing heads 5A and 5B to reproducing amplifiers 17a and 17b through head amplifiers 16a and 16b and the reproducing signal channel 9a and 9b, respectively. An operating power is transferred from a power supply amplifier 12 to the head amplifiers 16a and 16b through the power supply channel 10, a rectifying and smoothing circuit 14 and a regulator 15 disposed on the rotor.
The magnetic recording and/or reproducing apparatus has two recording heads and two reproducing heads. However, there is a magnetic recording and/or reproducing apparatus of multiple channel type that has more than two channels (for example, see Japanese Patent Examined Publication No. Hei 8-34025).
The magnetic recording and/or reproducing apparatus of multiple channel type disclosed in the above mentioned Publication has a plurality of reproducing heads arranged with pitches narrower than the widths of tracks. These reproducing heads reproduce signals from recorded tracks. A reproducing signal process circuit of the magnetic recording and/or reproducing apparatus processes the reproducing signals reproduced by the reproducing heads so as to generate reproducing signals that are free from tracking errors and so forth.
In recent years, the signal transfer frequencies of magnetic recording and/or reproducing apparatuses are becoming as high as several 100 MHz. In addition, their rotary drums are becoming miniaturized (for example as small as 18 mmφ).
As shown in FIG. 10, in order to decrease the number of channels of rotary transformer of the reproducing portion, one of output signals of the head amplifiers 16a and 16b that amplify reproduced signals from the reproducing heads 5A and 5B is selected by a switch 20 at timings of switching pulse signal shown in FIG. 4. The selected output signal is supplied to a reproducing amplifier 17 through one reproducing signal channel 9. In this example, the wirings of the reproducing portion on the rotor side of the rotary drum are structured as shown in FIG. 12 to FIG. 14.
Likewise, in order to decrease the number of channels rotary transformer of the recording portion, as shown in FIG. 11, the recording heads 4A and 4B are connected in series to one recording signal channel 8. In addition, head switches SW1a and SW1b that are turned off upon recording are connected to the recording heads 4A and 4B, respectively. Two recording signals A and B are transferred from a single recording amplifier 19 to the recording heads 4A and 4B, respectively, through one recording signal channel 8 (for example, see Japanese Patent Laid-Open Publication No. Hei 11-273183).
The wirings of the reproducing portion on the rotor side of the rotary drum shown in FIG. 12 are structured as follows. A wiring board 21 that has the head amplifiers 16a and 16b and a switch 20 are disposed between the reproducing head 5B and a lead wire portion of a rotor side coil 9r in the reproducing signal channel 9 of the rotary transformer 7. The reproducing heads 5A and 5B and the head amplifiers 16a and 16b are connected with wirings 23 and 24, respectively. A switch 20 is connected to a lead wire 22 of the coil 9r on the rotor side. In this example, since the wiring board 21 is disposed adjacent to the reproducing head 5B, the wiring 23 connected between the reproducing head 5A and the head amplifier 16a adversely becomes longer.
The wirings shown in FIG. 13 are structured in the manner that a lead wire portion of the coil 9r on the rotor side in the reproducing signal channel 9 of the rotary transformer 7 is disposed in a direction perpendicular to the reproducing heads 5A and 5B. The head amplifiers 16a and 16b and a lead wire 22 of the coil 9r on the rotor side are connected with wiring 23 and 24, respectively. The wirings shown in FIG. 14 are structured in the manner that a lead wire portion of the coil 9r on the rotor side in the reproducing signal channel 9 of the rotary transformer 7, the head amplifiers 16a and 16b, and a wiring board having a switch 20 are disposed in a direction perpendicular to the reproducing heads 5A and 5B. The reproducing heads 5A and 5B and the head amplifiers 16a and 16b are connected with wiring 23 and 24, respectively. A lead wire 22 of the coil 9r on the rotor side is connected to the switch 20. In the examples shown in FIG. 13 and FIG. 14, the length of the wiring 23 is the same as the length of the wiring 24. However, the total length of the wirings 23 and 24 shown in FIG. 13 and FIG. 14 is the same as that shown in FIG. 12.
Thus, with the wirings as shown in FIG. 12 to FIG. 14,
1) since the head amplifiers 16a and 16b, the rectifying and smoothing circuit 14, the regulator 15, and so forth are disposed along with the recording heads 4A and 4B and the reproducing heads 5A and 5B on the rotor side of the rotary drum, it is difficult to provide a space for the wiring board for a small diameter rotary drum of multiple channel type,
2) since the wirings become long, they result in inductance and capacity that prevent radio frequency signals from being transferred, and
3) since reproduced output signals are connected in series, even if the number of channels of the rotary transformer is decreased, noises of heads from which signals are not reproduced and amplifiers thereof adversely affect signals. As a result, the SNR (signal to noise ratio) becomes worse.
To solve the foregoing problem, what is needed is a rotary head drum apparatus for allowing wirings on the rotor side to become shorter. In addition, what is needed is a magnetic recording and/or reproducing apparatus of multiple channel helical scanning type using the rotary head drum apparatus.